Police in northern China's Inner Mongolia Autonomous Region managed to catch seven people suspected of poisoning 233 swans, Shanghai Daily reported.

The police spent nine days searching for the suspects and had caught them in Beijing and Tianjin municipalities as well as the provinces of Jilin and Hebei.

The swans were found dead in a lake in Zhenglan Banner, Xilingol League, and tests revealed that they were poisoned with Carbofuran, a type of pesticide, which was detected on the dead birds, according to the Zhenglan Banner government information office.

The local public security bureau has offered 100,000 yuan (about 14,770 U.S. dollars) to anyone who provides information on the identity of the suspected poachers, said Han Ruijin, deputy head of the bureau, on Wednesday.

In addition to the swans, 26 mallards were also found dead in the lake.